However, O’Toole holds a significant advantage against MacKay as a second choice among Lewis and Sloan backers.

While 55 per cent of Sloan supporters would back Lewis as second choice, 18 per cent of his backers would move to support O’Toole, while seven per cent would back MacKay. Twenty per cent of his supporters are either undecided or do not have a second choice.

Among Lewis supporters, more than 40 per cent would back O’Toole as a second choice, followed by 31 per cent who would move to support Sloan, and 13 per cent who would back MacKay. Slightly more than 15 per cent of Lewis’ supporters are either undecided or do not have a second choice.

The Conservative leadership race is determined by ranked ballot, meaning Sloan and Lewis supporters could influence the result of a final head-to-head contest with MacKay and O’Toole if the survey results hold true until the convention scheduled for later this year.

In the 2017 leadership race, Andrew Scheer narrowly defeated Maxine Bernier on the final, 13th ballot, despite Bernier placing first in the first 12 rounds of balloting.

The Mainstreet survey shows the two frontrunners polling close to each other across Canada, except in the Atlantic provinces, where MacKay has a nearly 33-percentage-point lead against O’Toole.

MacKay holds a 12-percentage-point lead among voters who are ages 18 to 40 compared to MacKay and an eight percentage point lead among those 65 and older. O’Toole has a narrow edge against MacKay for party supporters in age cohorts in between.

The poll is intended to represent the membership of the Conservative Party on the day that the survey was conducted.

The poll’s margin of error is plus or minus 2.62 per cent, 19 times out of 20.